Skin cancer is a significant and expensive public health problem, with ~5 million Americans treated at a cost of over $8 billion annually29. Melanoma is the deadliest skin cancer, and its incidence has more than tripled in the last four decades30,31. Indoor tanning (IT) is a well-established cause of melanoma and keratinocyte carcinomas8- 12,20-22,32. Indoor tanners are also more likely to experience sunburn3,4,33, a major risk factor for skin cancer9,14-19. Most tanners begin IT as teens or young adults31. In order to reduce IT and protect this at-risk population, IT is now being regulated in two ways. First, states restrict access by minors or require parental consent/accompaniment34. Second, the Food and Drug Administration (FDA) attempts to minimize harm from IT devices (e.g., protective eyewear, session duration limits)35. Although underutilized36, legislation such as age restrictions and taxation has been quite successful in decreasing engagement in other risky behaviors such as smoking37. Recent evidence suggests that more stringent IT laws such as age bans (vs. parent consent laws or no law) are associated with less youth IT38,39. Unfortunately, enforcement and compliance with IT laws are variable and inadequate28,40-44. When advocating for more stringent laws or enforcement, it is also important to attend to concerns about secondary effects that may be barriers to further restriction. These barriers include economic impacts of IT laws that may cause small businesses to organize and oppose progressive IT laws to protect their financial interests, and tanners switching to use IT beds outside of salons (e.g., homes, apartments, gyms) that are not well-regulated or inspected45-50. The goals of this five-year R01 are to use a mixed-method approach informed by the Multiple [Policy] Streams and RE-AIM51,52 Frameworks53 to investigate three specific aims. Aim 1 is a comparative case study to elucidate the IT legislation adoption process. Aim 2 uses a pseudo- patron (confederate) assessment, national survey, and archival data to investigate legislation implementation, i.e., regulation compliance in salons and non-salons and the association of compliance with policy stringency and enforcement provisions41 as well as IT and sunburn outcomes among adolescents and young adults. Aim 3 integrates data from the first two aims and external data to assess economic effects relevant to policy sustainability of IT stringency, enforcement, and compliance. The scientific premise derives from the paucity of research on the process of translating IT policy efforts into stringent IT legislation and compliance, as well as their effects54,55, such as positive outcomes on melanoma risk factors (IT, sunburns) and secondary effects (economic costs, compensatory tanning). Results of this comprehensive, multi-level, rigorous analysis will inform IT policy interventions as well as other health policy arenas and guide best practices for increasing IT law stringency, moving toward an IT ?endgame?56,57. These could include adding age bans to parental consent laws or increasing age bans to 19 or 21, similar to tobacco. As experts in the relevant content and methodologic domains, our Multiple-PI led team is well-poised to conduct this innovative, seminal research.